System for running tubular members

ABSTRACT

The present invention relates to a wiper plug and internal drop ball mechanism that may be used in conjunction with a downhole surge reduction tool to run, hang, and cement casing liners in a wellbore. The apparatus of the present invention comprises a wiper plug assembly removably attached to the drill string within the casing liner, a drop ball sub attached below the wiper plug assembly which releases a float valve actuator ball having a diameter larger than the drill string, and float equipment having a plurality of flapper valves. The apparatus of the present invention may further comprise a diverter tool connected between the drill string and the casing liner.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application is a continuation-in-part of U.S. patentapplication Ser. No. 10/337,404 filed Jan. 6, 2003, which was acontinuation of U.S. patent application Ser. No. 09/850,247 filed May 7,2001, which was a continuation-in-part of U.S. patent application Ser.No. 09/829,107 filed Apr. 9, 2001, now U.S. Pat. No. 6,491,103.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an apparatus for running tubularmembers such as drilling/production liners or subsea casing strings in awellbore. More particularly the present invention relates to a wiperplug and internal drop ball mechanism that may be used in conjunctionwith the running and cementing of such tubular members in a wellbore.

[0004] 2. Description of the Prior Art

[0005] In oilfield applications, a “casing liner,” “drilling/productionliner,” and a “subsea casing string” are tubular members which are runon drill pipe. The terms “casing liner” and “drilling/production liner”are usually used with respect to drilling operations on land, while theterm “subsea casing string” is used with respect to offshore drillingoperations. For ease of reference in this specification, the term“liner” is used to denote either a “casing liner,” a“drilling/production liner,” or a “subsea casing string.”

[0006] Prior art drop ball-actuated float equipment for use in cementingliners in place includes, for example, a float shoe or float collarwhich has one or more flapper valves and which is located at or near thebottom of the liner. The flapper valve or valves are conventionally heldopen by a breakable plastic tab which is actuated (i.e., broken) by adrop ball when the cementing operation is to begin. The industry hastraditionally used systems where a drop ball is released at the surface,and the drop ball must be small enough in diameter to pass through thesmallest restriction in the drill string, which usually is the diameterof the bore in the running tool. The size of such restrictions has,therefore, limited the maximum size of the opening in a float collar orshoe. In the case of a 13⅜″ liner, the maximum diameter of a drop ballis somewhere between 2 and 3 inches. Due to the small diameter bore oftraditional float equipment and the highly contaminated environment inwhich such equipment is used, the valves in traditional float equipmenttend to become plugged with cuttings and contaminants.

[0007] As a liner is lowered into the wellbore, the fluid in front ofthe liner must be displaced to flow through the opening in the floatequipment as well as around the outside annulus defined by the wellboreand the liner. The flow resistance of the two flow paths may be high andthus causes a pressure known as surge pressure to build up below theliner. This surge pressure can: (a) cause damage to the formation; (b)result in loss of expensive drilling fluid; and (c) result in the linersticking against the side of the borehole, which means the liner doesnot go to the bottom of the hole.

[0008] U.S. Pat. No. 5,960,881, which is incorporated herein byreference, discloses a downhole surge pressure reduction system toreduce the pressure buildup while running in a tubular member such as acasing liner. The system is typically located immediately above the topof the casing liner. Nonetheless, any plugging of the float equipment atthe lower end of the casing liner can, and very well may, render thesurge pressure reduction system of the '881 patent ineffective.

[0009] The method and apparatus according to the present inventionovercomes the plugging problem and allows enhanced passage of fluidthrough the tubular member and into the surge pressure reduction tool.

SUMMARY OF THE INVENTION

[0010] In accordance with the present invention, apparatus is providedfor running a tubular member through a wellbore containing drillingfluid using a drill string.

[0011] Apparatus in accordance with the present invention comprises arunning tool connected to the top of the tubular member having an axialbore therethrough.

[0012] Apparatus in accordance with the present invention furthercomprises a wiper plug assembly which includes a wiper plug releasablysuspended from a running tool within the tubular member and a receptaclesleeve to receive a drill pipe dart. During cementing operations, thewiper plug assembly receives the drill pipe dart and is released fromthe drill string at the top of the tubular member. The wiper plugassembly is then pumped downward forcing cement out of the bottom of thetubular member and into the annulus between the tubular member and theborehole.

[0013] One end of the wiper plug assembly is connected to the runningtool attached to the tubular member. The running tool for the wiper plugcomprises an axially indexing sleeve and a plurality of wedge-shapedfingers which releasably engage the wiper plug receptacle sleeve. Duringrunning in of the tubular member, the drilling fluid flows from thetubular member upward through the ports between the fingers and into thevoid above the wiper plug fins. To isolate the wiper plug fins frominternal pressure during cementing operations, the drill pipe sleeve isindexed axially downward to block the ports between the fingers.

[0014] Apparatus in accordance with the present invention also comprisesa drop ball sub attached to and below the wiper plug assembly within thetubular member. The drop ball sub releases a float equipment actuatorball which is larger in diameter than the smallest restriction in thedrill string. When released, the actuator ball drops to the bottom ofthe tubular member where it actuates float equipment. Once actuated,flapper valves in the float equipment prevent the back flow of cementtraveling downward through the tubular member.

[0015] Apparatus in accordance with the present invention may furthercomprise a surge pressure reduction device or diverter tool connectedbetween the drill string and the running tool. When the diverter tool isin an open port position, the drilling fluid may flow upward from insidethe diverter tool into the annulus between the casing cemented in placeand the drill string. When in a closed port position, the deviceprovides passage for fluid to travel downward through the drill string.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the accompanying drawings:

[0017]FIG. 1 is an elevation view of an, embodiment of the system of thepresent invention for running of a tubular member downhole.

[0018]FIG. 2 is an elevation view of an embodiment of the presentinvention illustrating flow path of the drilling fluid facilitatingsurge pressure reduction as tubular member is run downhole.

[0019]FIG. 3 is an elevation view of an embodiment of the presentinvention illustrating a drop ball seated in a yieldable seat of surgereduction apparatus with the ports of that apparatus in open position.

[0020]FIG. 4 is an elevation view of an embodiment of the presentinvention illustrating the surge reduction apparatus of FIG. 3 with theports of that apparatus in closed position.

[0021]FIG. 5 is an elevation view of an embodiment of the presentinvention illustrating second drop ball seated in yieldable seat of acollet finger sleeve with the ports in open position.

[0022]FIG. 6 is an elevation view of an embodiment of the presentinvention illustrating the collet finger sleeve blocking the colletfinger ports.

[0023]FIG. 7 is an elevation view of an embodiment of the presentinvention illustrating the drop ball seated in yieldable seat of a dropball sub apparatus with the port of that apparatus in open position.

[0024]FIG. 8 is an elevation view of an embodiment of the presentinvention illustrating a flapper valve actuator ball being forcedthrough a yieldable seat and drop ball sub apparatus with ports inclosed position.

[0025]FIG. 9 is an elevation view of an embodiment of the presentinvention illustrating the flapper valve actuator ball engaging a floatcollar.

[0026]FIG. 10 is an elevation view of an embodiment of the presentinvention illustrating a drop ball being pressured through yieldableseat in the drop ball sub apparatus.

[0027]FIG. 11 is an elevation view of an embodiment of the presentinvention illustrating a dart being pumped downhole behind cement.

[0028]FIG. 12 is an elevation view of an embodiment of the presentinvention illustrating the dart of FIG. 11 being pumped downward throughdrill string and engaging a seat in a wiper plug assembly.

[0029]FIG. 13 is an elevation view of an embodiment of the presentinvention illustrating a wiper plug assembly being wound downwardthrough a tubular member and forcing cement downward through floatequipment, out of tubular member, and upwards into annulus betweentubular member and formation.

[0030]FIG. 14A is an enlarged section view of the wiper plug assemblywith collet fingers engaging wiper plug upper flange.

[0031]FIG. 14B is an enlarged section view of the dart engaging wiperplug assembly with collet fingers moving radially inward and releasingwiper plug.

[0032]FIG. 15 is an elevation view of an embodiment of the presentinvention illustrating a dual wiper plug apparatus.

[0033]FIG. 16 is an enlarged section view of the latching mechanismconnecting the upper liner wiper plug to the lower liner wiper plug.

[0034]FIG. 17 is an enlarged section view of the latching mechanism asit releases the lower liner wiper plug from the upper liner wiper plug.

[0035]FIG. 18 is an elevation view of an embodiment of the presentinvention without an actuator ball sleeve illustrating flow path of thedrilling fluid facilitating surge pressure reduction as tubular memberis run downhole.

[0036]FIG. 19 is an elevation view of an embodiment of the presentinvention without an actuator ball sleeve illustrating the drop ballresting on the actuator ball with the collet finger sleeve blocking thecollet finger ports.

[0037]FIG. 20 is an elevation view of an embodiment of the presentinvention without an actuator ball sleeve illustrating a flapper valveactuator ball being forced through a yieldable seat.

[0038]FIG. 21 is an enlarged section view of the four plug embodiment ofthe present invention illustrating the drop ball seated in yieldableseat of a drop ball sub apparatus with the port of that apparatus inopen position.

[0039]FIG. 22 is an enlarged section view of the four plug embodiment ofthe present invention illustrating the drop ball seated in yieldableseat of a drop ball sub apparatus with the port of that apparatus inclosed position.

[0040]FIG. 23 is an enlarged section view of the four plug embodiment ofthe present invention illustrating a dart being pumped downward throughdrill string and engaging a seat in the lower liner wiper plug assembly.

[0041]FIG. 24 is an enlarged section view of the four plug embodiment ofthe present invention illustrating the latching mechanism as it releasesthe lower liner wiper plug from the upper liner wiper plug and movingaxially downward to engage the float equipment.

[0042]FIG. 25 is an enlarged section view of the four plug embodiment ofthe present invention illustrating actuator ball engaging the floatequipment.

[0043]FIG. 26 is an enlarged section view of the four plug embodiment ofthe present invention illustrating the actuator ball activating theflapper valves of the float equipment.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0044] A description of certain embodiments of the present invention isprovided to facilitate an understanding of the invention. Thisdescription is intended to be illustrative and not limiting of thepresent invention. In the appended claims, the term “tubular member” isintended to embrace either a “casing liner,” a “subsea casing string,”or a “drilling/production liner.”

[0045] With reference first to FIG. 1, the general components of asystem are illustrated in which apparatus in accordance with the presentinvention is used. A mast M suspends a traveling block TB. The travelingblock, in turn, supports a top drive TD which moves vertically on ablock dolly BD. An influent drilling fluid line L supplies the top driveTD with drilling fluid from a drilling fluid reservoir (not shown). Alaunching manifold LM connects to a drill string S. The drill string Scomprises numerous pipes which extend down into the borehole BH, and thenumber of such pipes is dependent on the depth of the borehole BH. Aflow diverting device B is connected between the bottom end of drillstring S and the top of running tool 162. A tubular member, such ascasing liner 161, is suspended from running tool 162. Float equipment,e.g. float collar 160, is fastened near the bottom of the casing liner161.

[0046] Solidified cement CE1 fixes a surface casing SC to thesurrounding formation F. The surface casing SC contains an opening O inthe uppermost region of the casing adjacent to the top. The opening Ocontrols return of drilling fluid as it travels up the annulus betweenthe drill string S and the surface casing SC.

[0047] Solidified cement CE2 fixes an intermediate casing IC to thesurrounding formation F. The intermediate casing IC is hung from thedownhole end of the surface casing SC by a mechanical or hydraulichanger H.

[0048] The annulus between the drill string S and the intermediatecasing IC is greater in area than the annulus between the casing liner161 and the intermediate casing IC. While the present invention is notintended to be limited to use in tight or close clearance casing runs,the benefits of the present invention are more pronounced in tightclearance running, since as the area is reduced and the pressure(pressure is equal to weight/area) is increased.

[0049] Referring now to FIG. 2, apparatus in accordance with the presentinvention comprises running tool 162 which is connected to the top ofcasing liner 161 and which has an axial bore therethrough. In oneembodiment of the present invention, a flow diverter tool B is removablyconnected between drill string S and running tool 162, and in anotherembodiment of the present invention, no such diverter tool is employed.Diverter tool B, when used, is preferably a diverter device as disclosedin the '881 patent. The diverter tool B comprises a housing 183 havingat least one housing flow port 169A, a yieldable seat 173, and a sleeve170 having at least one sleeve flow port 169B. When diverter tool B isin the “open port position,” sleeve 170 is arranged such that housingflow port 169A and sleeve flow port 169B are aligned. This providespassage for drilling fluid to flow from inside of housing 183 to annulusbetween drill string S and the cemented in place casing 205. When thediverter tool B is in the “closed port position,” sleeve 170 has beenindexed axially downward so that housing flow port 169A and sleeve flowport 169B are not axially aligned and the flow passage is blocked.

[0050] Wiper plug assembly WP is suspended inside casing liner 161 fromrunning tool 162 by the running tool S2 for the wiper plug, one end ofwhich is connected to running tool 162. As described in U.S. patentapplication Ser. No. 09/541,526, file Apr. 3, 2000, the wiper plug WP isreleasably connected to the second end of the running tool S2 by colletfingers 168. The openings or ports between collet fingers 168 providecommunication to the void above wiper plug fins 163. Drilling fluidflowing upward from drop ball sub 166 to flow diverter device B passesthrough the ports between collet fingers 168 and fills the void abovewiper plug fins 163. When casing liner 161 has been lowered to fulldepth, sleeve 171 may be indexed axially downward to block flow throughthe ports between collet fingers 168, thereby isolating the wiper plugfins 163 from internal pressure.

[0051] Drop ball assembly DB is attached to the bottom of wiper plugassembly WP. The drop ball assembly DB comprises a housing 166 having atleast one housing flow port 167A, a yieldable seat 175, a sleeve havingat least one sleeve flow port 167B, an actuator ball 201, and a secondyieldable seat 176. Before the release of actuator ball 201, sleeve 172is arranged in the “open port position” such that housing flow port 167Aand sleeve flow port 167B are aligned. These aligned ports provide apassage for drilling fluid to flow as discussed below.

[0052] Float equipment 160, which may for example be a float collar, islocated at or near the bottom of casing liner 161 and contains flappervalves which are actuated by the release of actuator ball 201. Thediameter of actuator ball 201 is greater than the smallest diameter inthe drill string and corresponds to the diameter of the bore of thefloat equipment. The diameter of the bore of the float equipment is alsogreater than the smallest diameter in the drill string.

[0053] Still referring to FIG. 2, in operation, apparatus in accordancewith one embodiment of the present invention is intended to be run downa borehole through drilling fluid while in the open port position. Inthe “open port position,” sleeve 170 of flow diverter device B (whenused), sleeve 171 of wiper plug assembly WP, and sleeve 172 of drop ballsub DB are positioned such that drilling fluid may follow flow path FPupward through the bore of float equipment 160. Following the flow path,drilling fluid then flows into the housing of drop ball sub DB aboveactuator ball 201 via aligned housing flow port 167A and sleeve flowport 167B, and through the bore in the wiper plug. Drilling fluid thenfills the void above the wiper plug fins 163 via the openings betweencollet fingers 168. The drilling fluid then flows through drill stringS2 and running tool 162, into diverter device B, and finally out ofdiverter device B into the annulus between drill string S and thecemented-in-place casing 205 via aligned flow hole 169A and flow port169B. The benefits of surge pressure reduction are thus provided.

[0054] In the embodiment of the present invention where no diverter toolis utilized, drilling fluid flows through drill string S2 and runningtool 162 and through drill string S.

[0055] Referring to FIG. 3, once the casing liner has been lowered tofull depth and cementing operations are ready to begin, a drop ball 200is dropped down drill string S and into yieldable seat 173 of flowdiverter device B. If a diverter tool is not used, the first landingpoint for drop ball 200 is yieldable seat 174. The diameter of drop ball200 is less than the smallest diameter of any restriction in drillstring S. For example, a 2¼ inch diameter drop ball may be used for adrill string with inside diameter of 3 inches.

[0056] Referring now to FIG. 4, drilling fluid is pressurized to apredetermined level above drop ball 200 such that sleeve 170 is movedaxially downward blocking housing flow holes 169A. The flow diverterdevice B is now in the “closed port position.”

[0057] Referring to FIG. 5, drilling fluid above drop ball 200 isfurther pressurized such that the yieldable seat 173 expands, and dropball 200 passes through yieldable seat 173 and lands in yieldable seat174 of collet finger sleeve 171. Drilling fluid is then pressurizedabove drop ball 200 such that sleeve 171 is moved axially downward whichcloses the ports formed by the spaces between collet fingers 168 asillustrated in FIG. 6.

[0058] Referring to FIG. 7, drilling fluid above drop ball 200 isfurther pressurized such the yieldable seat 174 expands and drop ball200 passes through expanded yieldable seat 174 and lands in seat 175 ofdrop ball sub 176. Drilling fluid is then pressurized to a predeterminedlevel above drop ball 200 such that sleeve 172 is moved axiallydownward. As sleeve 172 moves downward, the sleeve engages float valveactuator ball 201 and forces the ball through yieldable seat 176 asillustrated in FIG. 8.

[0059] With reference to FIG. 9, the float valve actuator ball 201 isreleased from drop ball sub 166 and moves downward toward the bottom ofcasing liner 161 where ball actuates flapper valves of float equipment160. Float valve actuator ball 201 then continues to bottom of casingliner 161 and exits casing liner 161 where it may subsequently begrinded into filings by downhole drill equipment.

[0060] With reference to FIG. 10, drilling fluid above drop ball 200 isfurther pressurized such that yieldable seat 175 is expanded and dropball 200 passes through the expanded seat 175, and exits casing linerwhere it may subsequently be grinded into filings by downhole drillequipment. At this time, the cementing operations are ready to commence.

[0061] With reference to FIG. 11, once cement pumping is complete, adrill pipe dart 202 is inserted into top of drill string S and displaceddownward by drilling fluid so that dart 202 establishes a barrierbetween drilling fluid and cement CE3. With reference to FIGS. 12 and14A, once the dart 202 reaches wiper plug assembly WP, the dart engagesa receptacle sleeve 182. The dart 202 conventionally comprises a nosesection with a barbed “shark tooth” profile “c-ring” for connection withreceptacle sleeve 182 and elastomer o-ring seals. The receptacle sleeve182 comprises a mating tooth profile for connection with the dart 202and a seal bore for receiving the O-rings. In this way, the dart 202 andreceptacle sleeve 182 form a sealed mechanical connection.

[0062] With reference to FIGS. 13 and 14B, a yieldable, disk-shaped flatwasher 181 supports dart receptacle sleeve 182 in the wiper plugassembly WP. Flat washer 181 is mounted in such a way that forceimparted by dart 202 is carried through the washer 181. As drillingfluid is further pressured above dart 202, the flat washer 181 yieldsand deflects slightly downward. The deflection of the flat washer 181allows the receptacle sleeve 182 to move slightly downward. The dartreceptacle sleeve 182 serves as a backup to collet fingers 168 formed onthe end of the drill string S2. The collet fingers 168 are formed suchthat their lower outer ends comprise wedge surfaces 179A, which arecaptured in a mating recess 179B in the top flange portion of the wiperplug assembly WP. As the dart receptacle sleeve 182 displaces downwarddue to the pressure above the dart 202, the radial support for thecollet fingers 168 is lost. The loss of radial support allows the wedgesurfaces 179A to force the collet fingers 168 radially inward therebyreleasing the wiper plug assembly WP from the drill string S2.

[0063] With reference still to FIG. 13, once released from drill stringS2, the wiper plug WP maybe pumped down the casing liner 161 therebydisplacing cement CE3 in the casing liner down through the flappervalves of float equipment 60. The flapper valves of the float equipment160 should prevent any “back-flow” or “u-tube action” of the cement.

[0064] Once the wiper plug WP has been pumped to the bottom of thecasing liner, the cement is allowed to harden, thereby completing thehanging and cementing job.

[0065] In another embodiment of the present invention, the drop ball subis used to launch an actuator ball without the sliding sleeve 172 (FIG.2). Referring to FIG. 18, the drop ball assembly DB is attached to thebottom of wiper plug assembly WP and comprises a housing 166 having aset of housing flow holes 167A, an actuator ball 201, and a yieldableseat 176. The set of housing flow holes 167A are sized to permit thecreation of a pressure differential between the annular space within thehousing 166 and the space outside the housing when drilling fluidpressure is increased above the actuator ball 201 to launch the actuatorball through the yieldable seat 176. In a preferred embodiment, the setof housing flow holes comprises four holes of 1 inch diameter size suchthat the actuator ball may be launched at a pressure differential ofapproximately 100 psi. However it is intended that the holes may besized to accommodate whatever pressure differential is required tolaunch the actuator ball.

[0066] With reference to FIG. 19, once drop ball 200 is used to move thesleeve 171 axially downward to close the ports formed by the spacesbetween collet fingers 168, drilling fluid above drop ball 200 isfurther pressurized such that the yieldable seat 174 expands and dropball 200 passes through expanded yieldable seat 174. The drop ball 200lands on top of the actuator ball 201 within the drop ball housing 166thus creating a clear bore through drill string S2. Drilling fluid isthen pressurized to a predetermined level above actuator ball 201 suchthat the actuator ball is forced through yieldable seat 176 asillustrated in FIG. 20. This is accomplished by pumping drilling fluidfrom the drill string into the drop ball housing 166 at a rate greaterthan the rate at which the drilling fluid can exit the housing via theset of flow ports 167A. This creates a pressure differential where thedrilling fluid pressure is greater within the drop ball housing 166 thanin the annular space between the drop ball housing and the casing liner161. When the drilling fluid pressure differential within the drop ballhousing 166 is increased to a predetermined level, the yieldable seatyields to launch the actuator ball from the drop ball housing. In apreferred embodiment, the yieldable seat 176 of the drop ball housing166 is fabricated to yield at a pressure differential of approximately100 psi.

[0067] With reference to FIG. 20, the float valve actuator ball 201 isreleased from drop ball sub DB and moves downward toward the bottom ofcasing liner 161 where ball actuates the flapper valves FC2 of floatequipment 160 as illustrated in FIG. 10. Float valve actuator ball 201and drop ball 200 then continue to bottom of casing liner 161 and exitcasing liner where they may subsequently be grinded into filings bydownhole drill equipment. At this time, the cementing operations areready to commence.

[0068] The foregoing has described what may be referred to as a “twoplug system” having one wiper plug and one dart which is used in therelease of the wiper plug. With reference to FIG. 15, another embodimentof the present invention comprises an upper liner wiper plug WP1 and alower liner wiper plug WP2. This type of system may be referred to as a“four plug system” since it comprises two wiper plugs and two drill pipedarts to release the wiper plugs.

[0069] The four plug system of FIG. 15 operates in substantially thesame way as the two plug system. In both the two plug system and thefour plug system, the apparatus is first run down a borehole until itreaches the required depth to hang a casing liner. At this depth, a dropball is pumped down the drill string into yieldable seat of drop ballsub. Drilling fluid pressure is increased behind the drop ball torelease an actuator ball from the drop ball sub to activate flappervalves of float collar.

[0070] With reference to FIG. 15, the four plug system comprises anupper liner wiper plug WP1 attached to drill string DS, a lower linerwiper plug WP2 attached to the upper liner wiper plug by releasemechanism (see FIG. 16), and a drop ball sub DB attached to the bottomof the lower liner wiper plug.

[0071] With reference to FIGS. 15 and 17, after the flapper valveactuator ball 310 is released, a first drill string dart 400 is pumpeddown the drill string and into casing liner CL where the first dartengages a lower liner wiper plug WP2. Drilling fluid pressure isincreased above the first dart 400 so that the lower liner wiper plugWP2 is released from an upper liner wiper plug WP1 and is pumpeddownward through the casing liner CL to displace contaminating drillingmud from the interior of the casing liner. At the bottom of the casingliner CL, drilling fluid pressure is further increased above the firstdart 400 so that the lower liner wiper plug latches to the float collarFC. Next, cement is pumped downward through the casing liner CL and intothe annulus between the borehole and the casing liner. Then, a seconddrill string dart (not shown) is pumped down the drill string and intothe casing liner CL where the second dart engages an upper liner wiperplug WP1. Drilling fluid pressure is increased above the second dart sothat the upper liner wiper plug WP1 is released from the drill string DSand is pumped downward through the casing liner CL to displace cementfrom the interior of the casing liner. At the bottom of the casing linerCL, drilling fluid pressure is again increased above the second dart sothat the upper liner wiper plug WP1 latches to the lower liner wiperplug WP2.

[0072] With reference to FIG. 16, the release mechanism for releasinglower liner wiper plug WP2 from upper liner wiper plug WP1 compriseslower liner fingers 301 having wedge-shaped ends 301A, upper linerfinger receivers 300 having wedge-shaped recesses 300A, a lower linerdart receptacle 302, and a sleeve 303 having radial protrusions 303A.Initially, the wedge-shaped ends 301A of lower liner fingers 301 engagethe wedge-shaped recesses 300A of upper liner fingers 300. Theprotrusions 303A of sleeve 303 prevent the lower liner fingers 301 frommoving radially inward and lock the wedge shaped-ends 301A in thewedge-shaped recesses 300A. The sleeve 303 is itself restrained by shearpins 304.

[0073] With reference to FIG. 17, a drill pipe dart 400, having adiameter less than the diameter of upper liner receptacle 305, isdropped into the drill string and lands in lower liner dart receptacle302. Drilling fluid pressure is increased above dart 400 to shear pins304 (shown in FIG. 16). Sleeve 303 is now unrestrained. Drilling fluidpressure is further increased above dart 400 to push sleeve 303 downwardso that protrusions 303A move below wedge-shaped ends 301A of lowerliner fingers 301. The lower liner fingers 301 are now free to moveradially inward to disengage with wedge-shaped recesses 300A of upperliner fingers 300. Drilling fluid pressure above dart 400 is increasedto pump the released lower liner wiper plug WP2 downward displacingdrilling mud from the inside walls of the casing liner CL. Once thelower liner wiper plug WP2 reaches the bottom of the casing liner CL,drilling fluid pressure is further increased above the dart 400 to latchthe lower liner wiper plug to float collar FC (shown in FIG. 15).Cementing operations may then be commenced.

[0074] With reference to FIG. 15, the upper liner wiper plug WP1 maythen be released from the drill string DS by following the sameprocedure described above to release wiper plug WP (shown in FIGS. 12,13, 14A, and 14B) in the two plug system. Once the upper liner wiperplug WP1 is pumped to the bottom of the casing liner CL and is latchedto the lower liner wiper plug WP2, the cement is allowed to harden,thereby completing the hanging and cementing job.

[0075] In another embodiment of the four plug system, before the floatequipment is activated, the lower liner wiper plug assembly is pumpeddownward such that the drop ball sub engages the float equipment andthen releases the actuator ball to activate the flapper valves of thefloat equipment. Referring to FIG. 21, before the release of the lowerliner wiper plug WP2, a drop ball 403 is dropped from the drill stringinto the yieldable seat 401 of the sliding sleeve 402. Drilling fluid isthen pressurized to a predetermined level above drop ball 403 such thatsleeve 402 is moved axially downward blocking the set of housing flowholes 167A. The drop ball sub DB is now in the “closed port position”(as shown in FIG. 22). Drilling fluid pressure is increased above thedrop ball 403 such that the seat 401 yields thereby permitting the dropball to pass through and land on the actuator ball 201. Cementingoperations can now commence.

[0076] With reference to FIG. 23, after the drop ball sub DB is set tothe closed port position, a first drill string dart 400 is pumped downthe drill string by cement and into casing liner CL where the first dartengages a lower liner wiper plug WP2. Cement pressure is increased abovethe first dart 400 so that the lower liner wiper plug WP2 is releasedfrom an upper liner wiper plug WP1 and is pumped downward through thecasing liner CL to displace contaminating drilling mud from the interiorof the casing liner. At the bottom of the casing liner CL, cementpressure is further increased above the first dart 400 so that the lowerliner wiper plug latches to the float collar FC.

[0077] Referring to FIG. 24, cement pressure is again increased to apredetermined level above the first dart 400 to release the first dart400 from engagement with the lower liner wiper plug WP2. The dart 400lands in the drop ball sub DB near the drop ball 403 and above theactuator ball 201.

[0078] Referring to FIG. 25, cement pressure is increased to apredetermined level above the actuator ball 201 to launch the actuatorball from the drop ball sub DB into the axial bore of the float collarFC. The actuator ball 201 lands in the seat FC3 of the actuating sleeveFC1 of the float collar FC.

[0079] Referring to FIG. 26, cement pressure is again increased to apredetermined level above the actuator ball 201 to displace theactuating sleeve FC1 from the bore of the float collar FC thus allowingthe flapper valves FC2 of the float collar to activate to any back-flowof the cement. The upper liner wiper plug is released and the cementingjob is completed as described above.

What is claimed is:
 1. A drop ball mechanism for use within a tubularmember being run on a drill string in a wellbore containing drillingfluid, comprising: a wiper plug assembly releasably connected to thedrill string within the tubular member near the top of the tubularmember; and a drop ball housing connected to the wiper plug assemblybelow the wiper plug assembly and having an axial bore therein and a setof flow holes formed therein for establishing communication between theaxial bore of the drop ball housing and the tubular member below thewiper plug assembly, said drop ball housing including a drop ball havinga diameter greater than the inside diameter of the drill string, saidset of flow holes having a diameter to permit the creation of a pressuredifferential between the axial bore of the drop ball housing and thetubular member below the wiper plug assembly when drilling fluid ispumped from the drill string into the drop ball housing, said pressuredifferential being of sufficient magnitude to cause the drop ball torelease from the drop ball housing.
 2. The drop ball mechanism of claim1, wherein the tubular member comprises float equipment attached to thetubular member near the bottom of the tubular member, said floatequipment having an axial bore through which drilling fluid may flow,said axial bore having a diameter greater than the inside diameter ofthe drill string, said float equipment including a plurality of flappervalves which are activated by the drop ball after it is released fromthe drop ball housing.
 3. The drop ball mechanism of claim 2, whereinthe wiper plug assembly has an axial bore therethrough and a receptaclein the axial bore for receiving a drill pipe dart.
 4. Apparatus forrunning a tubular member in a wellbore containing drilling fluid using adrill string, comprising: a running tool connected to the top of thetubular member and having an axial bore therethrough; float equipmentattached to the tubular member near the bottom of the tubular member,said float equipment having an axial bore therethrough which drillingfluid and cement may flow, said axial bore having a diameter greaterthan the inside diameter of the drill string, said float equipmentincluding a plurality of flapper valves; a wiper plug assemblyreleasably connected to the drill string within the tubular member nearthe top of the tubular member, said wiper plug assembly having an upperend, a lower end, and an axial bore formed therethrough, said wiper plugassembly having a receptacle in said axial bore for receiving a drillstring dart to release the wiper plug assembly from the drill string andto move the wiper plug assembly downward to engage the float equipment;and a drop ball mechanism connected to the lower end of the wiper plugassembly, said drop ball mechanism including a releasable drop ballhaving a diameter greater than the inside diameter of the drill string,said drop ball being released to activate the flapper valves of thefloat equipment once the wiper plug assembly engages the floatequipment.
 5. The apparatus of claim 4, wherein the drop ball mechanismfurther comprises a drop ball housing for releasably connecting the dropball to the lower end of the wiper plug assembly, said drop ball housinghaving a set of flow holes formed above the drop ball through whichdrilling fluid may flow into the bore of the wiper plug.
 6. Theapparatus of claim 5, further comprising a diverter tool connectedbetween the drill string and the running tool, said diverter tool havingan open port position and a closed port position, said diverter toolbeing in the open port position during the running in of the tubularmember.
 7. The apparatus of claim 4, wherein the diverter toolcomprises: a housing connected to the drill string, said housing havinga set of housing flow holes formed therein; a sleeve within the housinghaving a set of sleeve flow ports formed therein; said sleeve beinginitially positioned within the housing such that an open port positionexists; a yieldable drop ball seat connected to the sleeve; and an axialindexing means to move the sleeve between the open port position and theclosed port position.
 8. The apparatus of claim 4, further comprising awiper plug release mechanism for releasing the wiper plug from the drillstring, said release mechanism comprising: a plurality of fingers whichare formed on the end of the drill string such that an opening existsbetween each adjacent finger, said fingers having lower outer ends thathave wedge-shaped surfaces for engagement with the dart receptacle ofthe wiper plug; and a yieldable, circular flat washer in the wiper plugwhich supports the receptacle and which allows the fingers to disengagefrom the receptacle when the dart is received and when pressure isincreased behind the dart.
 9. Apparatus for running a tubular member ina wellbore containing drilling fluid using a drill string, comprising: arunning tool connected to the top of the tubular member and having anaxial bore therethrough; float equipment attached to the tubular membernear the bottom of the tubular member, said float equipment having anaxial bore therethrough which drilling fluid and cement may flow, saidaxial bore having a diameter greater than the inside diameter of thedrill string, said float equipment including a plurality of flappervalves; an upper liner wiper plug assembly having an upper end which isreleasably connected to the drill string within the tubular member nearthe top of the tubular member, a lower end, and an axial bore formedtherethrough, said upper liner wiper plug assembly including areceptacle in said bore for receiving a drill string dart; a lower linerwiper plug assembly having an upper end which is releasably connected tothe lower end of the upper liner wiper plug assembly, a lower end, andan axial bore formed therethrough, said lower liner wiper plug assemblyincluding a receptacle in said bore for receiving a drill string dart torelease the lower liner wiper plug assembly from the drill string and tomove the lower liner wiper plug assembly downward to engage the floatequipment; and a drop ball mechanism connected to the lower end of thelower liner wiper plug assembly, said drop ball mechanism including areleasable drop ball having a diameter greater than the inside diameterof the drill string, said drop ball being released to activate theflapper valves of the float equipment once the lower liner wiper plugassembly engages the float equipment.
 10. The apparatus of claim 9,further comprising a diverter tool which is connected between the drillstring and the running tool, said diverter tool having an open portposition and a closed port position, said diverter tool being in theopen port position during the running in of the tubular member.
 11. Theapparatus of claim 10, wherein the diverter tool comprises: a housingwhich is connected to the drill string, said housing having a set ofhousing flow holes formed therein; a sleeve within the housing having aset of sleeve flow ports formed therein, said sleeve being initiallypositioned within the housing such that an open port position exists; ayieldable drop ball seat which is connected to the sleeve; and an axialindexing means to move the sleeve between the open port position and theclosed port position.
 12. The apparatus of claim 10, wherein the upperliner wiper plug is releasably connected to the drill string by amechanism which comprises: a plurality of fingers which are formed onthe end of the drill string such that an opening exists between eachadjacent finger, said fingers having lower outer ends that havewedge-shaped surfaces for engagement with the dart receptacle of theupper liner wiper plug; and a yieldable, circular flat washer in theupper liner wiper plug which supports the receptacle and which allowsthe fingers to disengage from the receptacle when the dart is receivedand when pressure is increased behind the dart.